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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Until relatively recently, it was generally believed that hypomagnesemia was a rare entity in clinical practice. It is clear, however, from newer studies that the overall incidence of hypomagnesemia in hospitalized patients can range from 7 to 52%. The greatest association of hypomagnesemia in hospitalized patients appears to be in hypokalemic states and in patients confined to intensive care units. Most of these patients demonstrate cardiovascular abnormalities, ranging from cardiac arrhythmias and atrial fibrillation to hypertension. On the basis of primarily epidemiologic and experimental findings, it has been suggested that there may be a strong association between the dietary intake of Mg (and errors in the Mg metabolism and distribution of Mg in the body), the concentration of this element in the myocardium and blood vessels, and the risk for development of cardiac arrhythmias, sudden death ischemic heart disease, hypertension, transient ischemic attacks, strokes and pre-eclampsia-eclampsia. During the past 5-6 years, a considerable amount of new, quantitative clinical evidence has been found which lends considerable support to these tenets. Clinical trials utilizing Mg as a therapeutic tool to treat refractory arrhythmias, digitalis toxicity-associated arrhythmias, myocardial infarctions, diabetic angiopathy, transient ischemic attacks, cerebral resuscitation, hypertension and 'classical' migraine are under way, and to an extent have been successful. Careful assessment of serum, blood cells, and urine for free versus bound Mg should be done routinely in cardiovascular disease and high-risk patients.
Magnesium 1985
PMID:New perspectives on the role of magnesium in the pathophysiology of the cardiovascular system. I. Clinical aspects. 391 80

It has generally been believed that the physiological roles for magnesium ions (Mg2+) in cardiac and vascular smooth muscle are limited to regulation of contractile proteins, sarcoplasmic reticular membrane transport of calcium ions (Ca2+), cofactor in ATPase activities and metabolic regulation of energy-dependent cytoplasmic and mitochondrial pathways. In addition, up until recently, it was not thought that small changes in free external ([Mg2+]0) or cytoplasmic Mg2+ could exert any significant effects on cardiac or vascular smooth muscle contractility. It is clear, however, from the newer studies that [Mg2+]0 can affect tension and contractility of these muscle cells by altering membrane and intracellular organelle binding and transport of Ca2+, affecting hormone-receptor interactions, regulating electrolyte content and transport, affecting resting membrane-generated and action potentials, altering excitation-contraction coupling events, and regulate peripheral and cerebral vascular tone and blood flow. In addition, it is also now clear that small changes of free [Mg2+] at the cardiac and vascular muscle membranes can exert significant effects on mechanical and electrical activities of these cells. Considerable new data lend support to the idea that [Mg2+]0 is fundamental in the regulation of cardiovascular homeostasis. Dietary, metabolic or drug-induced changes in Mg2+ levels appear to play important roles in the etiology of cardiac and vascular disorders. Evidence is reviewed and presented to indicate that Mg2+ is important in the pathophysiology and treatment of certain forms of experimental and genetic types of hypertension. This divalent cation may also be important in the etiology of a variety of disorders which have vasospasm in common. Evidence is reviewed to support the concept that Mg2+ is a naturally occurring or mimic weak Ca2+ antagonist, which should be useful in the treatment of several types of cardiac and vascular disorders.
Magnesium 1985
PMID:New perspectives on the role of magnesium in the pathophysiology of the cardiovascular system. II. Experimental aspects. 391 81

Magnesium, calcium and zinc determinations were performed by flame absorption spectrophotometry and induced coupled plasma on the red blood cells (RBC) and plasma (P) of spontaneously hypertensive (SHR) and control (WKR) male rats, aged of 45 to 158 days. The blood sampling was done by cardiac puncture after ether anaesthesia. SHR rats have lower RBC and P Mg values and higher RBC Zinc values than WKR. These differences are very significant (P less than 0.002 to P less than 0.0001) among the animals aged of 96 days or more. When compared to the data of the literature, these results confirm the existence of associations between hypertension, low blood Mg and high RBC Zn values but reveal only minor changes in RBC Ca concentrations.
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PMID:[Magnesium, calcium and zinc levels in plasma and erythrocytes of spontaneously hypertensive rats]. 392 69

Subcellular membrane fractions were isolated from mesenteric arteries and vas deferens of salt-resistant and salt-sensitive Dahl rats on low-salt (0.4% NaCl) high-salt (8.0% NaCl) diets. Only the salt-sensitive Dahl rats on the high-salt diet developed sustained high blood pressure (BP) after 5 weeks of the high-salt diet. Protein contents, membrane associated enzyme activities, calcium ion (Ca2+) binding and ATP-dependent CA2+ transport were compared in fractions isolated from all four groups. No obvious changes were observed, except for minor enhancement in magnesium ion (Mg2+)- and CA2+ ATPase activities of mesenteric arterial membranes isolated from salt-sensitive Dahl rats on high-salt diet compared to those from other groups of rats. The membrane fractions from vas deferens of salt-sensitive Dahl rats on the high-salt diet, on the other hand, showed decreased ATP-dependent Ca2+ transport compared to those from salt-sensitive Dahl rats on the low-salt diet. No difference was observed in membrane fractions isolated from salt-resistant Dahl rats on high-salt diet compared to those on low-salt diet. The significance of these observations are discussed in relation to the findings previously obtained from corresponding smooth muscle tissues of spontaneous hypertensive rats (SHR).
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PMID:Subcellular membrane properties in vascular and non-vascular smooth muscles of Dahl hypertensive rats. 395 84

Magnesium (Mg) is a vasodilator which may play a role in the regulation of blood pressure. The present study measured tissue Mg and calcium (Ca) levels in a hypertension model, the spontaneously hypertensive (SHR) rat, using the Wistar-Kyoto rat as a control. Mean serum Mg levels were normal in both types of rats. In SHR rats given H2O ad libitum, four of nine tissues (kidney, heart, lung, bone) had significant 6-16% decreases in Mg content (less than 0.025-0.0005). In SHR rats undergoing chronic saline diuresis, seven of nine tissues (liver, kidney, testis, heart, lung, spleen, bone) had significant 7-18% decreases in Mg content. Tissue Ca in these same rats was significantly decreased by 6-39% in four of nine tissues, but was increased in other tissues. These observations indicate that both Mg and Ca depletion can occur in selected tissues in SHR rats and the number of tissues with Mg depletion doubles during chronic saline diuresis. If Mg depletion is also found in the vascular smooth muscle of this hypertension model, it may be a contributory factor in the hypertension.
Magnesium 1986
PMID:Tissue magnesium in spontaneously hypertensive rats. 395 95

Water hardness can no longer be considered as the most reliable "water factor' with regard to the cardiovascular risk observed in epidemiologic studies. Only two out of three studies have shown a reverse correlation between cardiovascular mortality and water hardness. But studies carried out on the water Mg level alone, as opposed to those on water hardness (Ca + Mg) have all shown a reverse correlation between cardiovascular mortality and the Mg level. In developed countries, the Mg intake is often marginal and the Mg intake coming from drinking water represents the critical factor through which the Mg intake is deficient or satisfactory. Thus, Mg deficiency, either experimental or in man facilitates cardiovascular pathology. The importance of the Mg intake in drinking water is both quantitative and qualitative. Water containing Mg is better and more quickly absorbed than dietary Mg. This particular availability might help to understand why an adequate water Mg level may determine a better state of health, even without any Mg deficiency. Epidemiological data in man and experimental data in rats have demonstrated that the intake of water containing a sufficient amount of Mg may prevent arterial hypertension and correlated ionic and nervous disturbances. Indirectly the water Mg level also interferes in the leakage of food-borne Mg during cooking. There is an inverse correlation between the Mg loss in the cooked food and the Mg level of the cooking water itself. Mg appears to be an antagonist of noxious polluting agents (e.g. in the human amnion, Mg is a competitive inhibitor of Pb and Cd). It is not advisable to enrich water in Mg in the course of the processing since its corrosivity index would also increase. The best pathway is probably to neutralize corrosive water by filtration on calibrated grains of earth-alkaline metals (Neutralite or Magno or Akdolit) to ensure the highest possible Mg/Ca ratio, with the best anticorrosive power.
Magnesium 1985
PMID:Magnesium level in drinking water and cardiovascular risk factor: a hypothesis. 403 5

Renal excretion, skeletal muscle content and plasma concentration of electrolytes were studied in 108 patients on long-term diuretic therapy for congestive heart failure and/or arterial hypertension. As reference populations served a group of 16 healthy volunteers and a group of 22 patients with liver cirrhosis, but not on diuretic therapy. Diuretic therapy was found to deprive the patients of their ability to conserve potassium and magnesium when there was a simultaneous cellular depletion of these ions. Magnesium excretion was found to be correlated to the skeletal muscle magnesium content. An inverted Na/K ratio in urine and a low magnesium excretion were fair indicators of cellular magnesium depletion.
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PMID:Renal excretion of electrolytes in patients on long-term diuretic therapy for arterial hypertension and/or congestive heart failure. 409 Oct 44

Bovine hypothalamus contains a stable, low molecular weight substance with ouabain-like properties. To further study its mechanism of action and potential physiological importance we examined its effects on purified Na+-K+-ATPase in a kinetic coupled-enzyme assay. Under optimal conditions up to 95% of Na+-K+-ATPase activity could be inhibited by the factor. Mg2+ is required for maximal inhibitory activity, but ligand requirements for optimal activity are otherwise distinct from those of both ouabain and vanadate. Inhibition is reversed by high concentrations of sodium chloride plus EDTA. Kinetic analysis yielded a Ki = 1.4 nM. The hypothalamic factor is a high-affinity reversible inhibitor of Na+-K+-ATPase, being at least as potent as the cardiac glycoside ouabain and may be a circulating inhibitor of sodium transport, which appears to be associated with experimental volume-expanded hypertension and human essential hypertension.
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PMID:Hypothalamic sodium-transport inhibitor is a high-affinity reversible inhibitor of Na+-K+-ATPase. 609 82

Hypercalcemic conditions are commonly associated with hypertension and with abnormal magnesium homeostasis. The mechanism by which the hypertension of hypercalcemia is mediated is not clear, and the role that magnesium may play in its generation has not been examined. We review here the available clinical and experimental data and propose a role for abnormal magnesium metabolism in the mediation and generation of the hypertension of hypercalcemia.
Magnesium 1984
PMID:The possible role of magnesium in hypercalcemic hypertension. 609 41

Plasma and erythrocyte Na+ and K+ and erythrocyte membrane (EM) Na+, K+ ATPase, Mg2+ ATPase and Ca2+, Mg2+ Atpase activities were studied in four groups of women -- non-pregnant, normal pregnant, with pregnancy edema (PE) and with pregnancy induced hypertension (PIH). The effect of diuretic therapy in PE and PIH was also evaluated. Plasma Na+ concentration was higher in PE and PIH. There was a significant reduction in (Na+ + K+) ratio between cell and plasma in these two groups. EM Na+, K+ ATPase was unaltered in PE and PIH. The Mg2+ ATPase was elevated by 44% in PE and by 100% in PIH subjects. There was a 50% reduction in Ca2+, Mg2+ ATPase activity in PE. Diuretic therapy had no effect either on electrolyte levels or on any of the EM ATPases. From these results it may be concluded that Na, K, ATPase -- which in kidney is a site of action for furosemide, a potent diuretic -- is unaffected in PE and PIH and, hence, treatment with diuretics -- is unaffected in PE and PIH and, hence, treatment with diuretics in such patients may be ineffective.
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PMID:A study of erythrocyte membrane cation transport adenosine triphosphatases in pregnancy-induced hypertension and of in vivo effects of diuretic treatment. 611 3


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